The flow of current through wires and the opening and closing of electrical switch contact create sources of radiation that can be detected by remote equipment. As a result, data created by the opening and closing of electrical switch contacts is remotely detectable. Because such data is remotely detectable, systems that use switches with mechanical contacts either lack privacy, or such systems must be enclosed in housings designed to shield the system so as to prevent the detection of the radiation that is produced when electrical switch contacts are opened and closed. In recent years, communication, control and sensing networks using fiber optic components have been developed. Such networks have the advantage that they do not generate electromagnetic fields and the radio frequency waves associated with such fields. In order for optically based communication, control and sensing networks to be fully secure from remote data detection, it is necessary that the switching elements of such networks be optically based, rather than electro-mechanical based, i.e., comprises mechanical contact switches.
Most existing optically based switches use an amplitude threshold detection technique to denote the "open" and "closed" status of a switch. Unfortunately, variations in optical losses (at connectors in particular) make establishing a threshold detection level for an amplitude modulated optical switch difficult. The present invention is directed to providing optically based switches and networks of such switches that overcome this disadvantage. More specifically, the present invention is directed to providing an optically based switch having an output that accurately denotes the "open" and "closed" status of the switch.